To make sharp (in various transferred senses of the adjective). = sharpen, v. 2b.

To make sour or acid; esp. to cause to have a tart or sour taste; to spoil in this way.

transitive. To intermix sourness in or with.

(un-, prefix2 affix 1d(c).)

transitive. To turn (milk, beer, etc.) slightly sour.

transitive. To deprive of sweetness; to unsweeten.

To make sharp or sharper (in various transferred and figurative senses of the adjective). Now… To give an acid flavour or quality to, to make (a…

transitive. To make slightly acidic or sour; to add an acidic substance to (food); also figurative. Frequently in passive.

transitive and intransitive. To turn sour; to curdle.

transitive. figurative. To transform into something sour or acid. Obsolete. rare.

transitive. To taint, infect; ? to tinge, stain; dialect to give a smack or tang to.

To affect with sharpness or acidity. rare.

transitive. To treat with acid, to acidify; spec. to inject acid into (a well) in order to enlarge pores in the surrounding rock and stimulate…